Multiple contact sprockets

ABSTRACT

A SPROCKET WHEEL HAVING TWO SURFACES OF CONTACT FOR CONTACTING THE SAME ROLLER OF SPROCKET CHAIN. ONE OF THE CONTACT SURFACES CONSISTS OF AN ELASTIC MATERIAL AND CONTACTS THE ROLLER BEFORE THE OTHER CONTACT SURFACES. THIS IS BECAUSE THE ONE CONTACT SURFACE EITHER IS OUT OF PHASE WITH THE OTHER CONTACT SURFACE OR HAS A LARGER BOTTOM DIAMETER THAN THE OTHER CONTACT SURFACE. A CHAIN DRIVE SYSTEM USES A DRIVING WHEEL HAVING ONE ROW OF SPROCKETS FORWARDLY OUT OF PHASE OF ANOTHER ROW AND A DRIVEN WHEEL HAVING ONE ROW OF SPROCKETS REARWARDLY OUT OF PHASE WITH ANOTHER ROW.

Sept. 20, 1971 vosHlAKl suGlMoTo MULTIPLE CONTACT SPROCKETS I 3. sheets-smet 1 Filed sept. a,i 1969 F IG.

m' MM mdf/M 1 y y f ATTORNEYS Sept 20 l971 YcsHlAkl suc-:IMoTo 3,605,513

*I MULTIPLE CONTACT SPROCKETS 3 Sheets-Shore?. 2

med sept.` a, 1969 ZMMw/ff ATTORNEYS SePf- 20, 1971 YosHlAKl suGlMo'ro 3,605,518

HULTIPLE CONTACT SEROGKETS Filed Sept. 8. 1969 3 Sheets-Sheet 5 Flan i f Fls ATTORNEYS United States Patent Oice 3,605,513 MULTIPLE CONTACT SPROCKETS Yoshiaki Sugimoto, Tokorozawa, Saitama Prefecture, Japan, assignor to The Tsubakimoto Chain Mfg. Co.,

Ltd., Osaka, Japan Filed Sept. 8, 1969, Ser. No. 856,059 Claims priority, application Japan, Sept. 17, 1968, 43/67,115, 43/67,116 Int. Cl. F16h 55/14, 55/18, 55/30 U.S. Cl. 74--243PC 10 Claims ABSTRACT OF 'I'HE DISCLOSURE A sprocket wheel having two surfaces of contact for contacting the same roller of sprocket chain. One of the contact surfaces consists of an elastic material and contacts the roller before the other contact surfaces. This is because the one contact surface either is out of phase with the other contact surface or has a larger bottom diameter than the other contact surface. A chain drive system uses a driving wheel having one row of sprockets forwardly out of phase of another row and a driven wheel having one row of sprockets rearwardly out of phase with another row.

BACKGROUND OF THE INVENTION This invention relates to sprocket wheels, and in particular to sprocket wheels used in high speed chain drives.

A well-known method of mechanical power transmission involves the use of a chain drive wherein power is transmitted from a driving shaft to a first sprocket wheel mounted thereon and through a chain to a second sprocket wheel mounted on a driven shaft. In such chain drive systems, collisions occur between the chain rollers and the tension surfaces of the sprockets of the driving sprocket wheel. These collisions create noise and vibration which in the past have been considered unavoidable. Furthermore these collisions expend energy causing wear and fatigue of the sprockets and of the chain rollers and roller bushings. Such Wear and fatigue results in undesirable break downs and in high maintenance costs. These collisions are aggravated by a slack drive chain.

With these disadvantages in mind, it is an object of this invention to provide an improved sprocket wheel which cushions these collisions and thereby eliminates noise and vibration and prevents the undesirable expenditure of energy.

Itis a further object of this invention to provide a multirow sprocket wheel which performs these functions.

It is a still further object of this invention to provide an improved chain drive system employing both driving and driven sprocket Wheels which cushion the sprockets and the chain due to the slack of the chain.

In accordance with the present invention these objects are accomplished by the provision of a sprocket having two surfaces of contact with each chain roller. One of said surfaces is adapted to contact the roller prior to the other of said surfaces and is formed of an elastic material. In one embodiment of the invention, the sprocket wheel has two rows of sprockets, one of said rows being forwardly out of phase with the other of said rows, thereby providing the two surfaces of contact. In a second embo'diment of the present invention, the sprocket Wheel has two rows of sprockets, one of said rows having a different bottom diameter than the other of said rows to form the two surfaces of contact. Either of the said embodiments may comprise a sprocket wheel having a single row of sprockets, the sprockets being divided in the direction of their widths to form the two surfaces of contact. Furthermore, in either of said embodiments more than two rows of sprockets may be provided. Each row may be 3,605,513 Patented Sept. 20, 1971 adapted to successively contact the chain roller, the number of contact actions being equal to the number of rows. However, this becomes impractical with a large number of rows. Each alternate row may have the same Contact surface, there then being two contact actions. Or any desired contact sequence may be employed.

Other objects will become apparent from the following detailed description, taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a sprocket chain used in conjunction with the present invention;

FIG. 2 is a partial side view of a sprocket wheel of a first embodiment of the present invention;

FIG. 3 is a sectional view taken along line 3 3 of FIG. 2;

YFIG. `4 is similar to FIG. 3 but of a slightly modified sprocket wheel;

FIG. 5 is a schematic view of the sprocket wheel of FIG. 2 used in a power drive system;

FIG. 6 is a partial side view of a sprocket wheel of a second embodiment of the present invention;

FIG. 7 is a sectional view taken along line 7-7 of FIG. 6;

FIG. 8 is similiar to FIG. 7 but of a slightly modified sprocket wheel;

FIGS. 9 and 1() are top and side views, respectively, of a multi-row sprocket wheel according to the first ernbodiment of the present invention;

FIGS. 11 and 12 are top and side views, respectively, of a multi-row sprocket wheel according to the second embodiment of the present invention; and

FIG. 13 is a partial section view of a single row sprocket wheel of the second embodiment of the present invention.

Referring to FIGS. 1 and 2, a novel sprocket wheel embodying the present invention is designated generally by 1 and a mating drive chain by 2. Drive chain 2 has a number of rollers, each having portions 9 -and 10. A first row of sprockets 3` having Contact surfaces 4 are .forwardly out of phase by angle et, i.e. forwardly in the direction of rotation of the sprocket wheel 1 as shown by the arrow, with a second row of sprockets 5 having contact surfaces 6. The Contact surfaces 4 of sprockets 3 comprise an elastic material 7 to be hereinafter described in detail.

The angle a is the relative phase difference between the two rows of sprockets, and its value is dependent upon the mechanical properties and the shape of both the elastic surface and the metallic body of the sprocket.

The a in radian may be calculated by the fonmula below:

:1R aR a wherein P--Pitch of chain R=Radius of the pitch circle N=Number of teeth The surface 4 may be provided with elastic material in any convenient manner. FIG. 3 shows sprocket wheel 1 partially in cross-section wherein elastic material 7 comprises a coating and the remainder of the sprocket wheel is a metal base 8. When this arrangement is used, the coating must at least be as thick as the difference in phase between the rows of sprockets.

FIG. 4 shows an arrangement similar to that of FIG. 3, but wherein the entire row of forwardly phased sprockets 3 consists of elastic material 7, and the other row of sprockets v5 consists of metal base 8i.

Referring again to FIG. 2, the operation of this embodiment of the invention will be explained. As sprocket wheel 1 drives chain 2, portion 10 of a chain roller contacts with surface 4 of one of the forwardly phased sprockets 3. The elastic material 7 is deformed until portion 9 (dashed lines) contacts surface 6` of the lagging sprocket 5.

This operation allows the force of collision between sprocket wheel 1 and chain 2 to be `absorbed by elastic material 7. The reaction force received by the sprockets from chain 2 is first applied to sprocket f3. Then, when elastic material f7 is deformed until phase angle fr becomes zero, to sprocket 5 and metal base y8i. Since elastic material 7 absorbs the initial force of collision, the reaction force between chain 2 and sprocket wheel #1 is essentially all transmitted to metal base 8. This arrangement both reduces noise and vibration and increases chain and sprocket life by eliminating metal to rmetal collisions and by providing the absorbing action of the elastic material.

PIG. 5 discloses au arrangement of this embodiment of the invention wherein the consequences of a slack chain are overcome. In practice, the actual length of the chain is made longer than theoretically necessary to facilitate the mounting of the chain over the sprockets. But, the resultant slack chain accentuates the problems of noise, 'vibration and collision.

In FIIG. 5 the sprocket wheel 1 of FIG. 2 is the driving Wheel, and ra sprocket wheel 11 is the driven wheel. Chain 2 is made longer than necessary as explained above. Wheel l has one row of sprockets 3 forwardly phased from a second row of sockets 5, thereby absorbing collisions between driving wheel 1 and chain 2. However, driven wheel 11 has a -rst row of sprockets 3, aligned with sprockets 3, which are rearwardly out of phase from a second row of sprockets 5, aligned with sprockets 5.

Therefore, collisions between chain 2 and driven wheel 11 are absorbed in a like manner to the collisions between driving Wheel 1 and chain 2.

FIG. 6 shows a second embodiment of applicants invention. Sprocket wheel 211 comprises a first row of sprockets 23 having contact surfaces 24, and a second row of sprockets 25 having contact surfaces 26. The bottom diameter of sprockets 23 is greater than the bottom diameter of sprockets 25. The contact surfaces 24 of sprockets 23 comprise an elastic material 27 to be hereinafter described in detail.

The difference (Ad) of the bottom diameters is usually denoted relative to the radius of the standard tooth root R, and to be in the range as a`=bottorn diameter of the standard tooth. This value depends on the mechanical property of elastic material, and the shape of both the elastic surface and the metallic body of the sprocket.

As is the case Iwith the first embodiment of the invention, the surface 24 rmay be provided with elastic material 27 in any convenient manner. FIG. 7 shows sprocket wheel 21 partially in cross-section wherein elastic material 27 comprises a coating and the remainder of the sprocket Wheel is metal base 28. When this arrangement is used, the coating must be at least as thick as the difference in bottom diameters between the rows of sprockets.

FIG. 8 shows an arrangement similar to that of FIG. 7, but wherein the entire row of sprockets 23 consists of elastic material 27, and the other row of sprockets 25 consists of metal base 28.

Referring again to FIG. 6, the operation of this embodiment of the invention will be explained as sprocket wheel 21 drives the chain, portion 10 of a chain roller contacts surface 24 of one of the sprockets 23. The elastic material 27 is deformed until portion 9 (dashed lines) contacts surface 26 of the sprocket 25.

The force of collision between sprocket wheel and the chain is thereby absorbed by the elastic material 27, and the reaction force is received by the metal base 28 in a manner similar to that described with regard to the first embodiment, thereby reducing noise and vibration and increasing chain and sprocket life.

FIGS. 9 and l0 show a multi-row sprocket wheel of the first embodiment of the invention. The sprocket wheel has tive rows of sprockets 31, 32, 33, 34 and 35. Rows 31 and 34 having a coating of elastic material 36 are phased forwardly of rows 32 and 33 by u1 and row 35, also having a coating of elastic material 36, is forwardly phased from rows 32 and 33 by a2, a2 being approximately twice al. The sprocket wheel of FIGS. 9 and l0 will thusly have three contact actions with a chain roller, first by sprockets 35, then lby sprockets 31 and 34 ,and last by sprockets 32 and 33.

FIGS. l1 and 12 show a multi-row sprocket wheel of the second embodiment of the invention. This sprocket Wheel also has five rows of sprockets 41, 42, 43, 44 and 45. Row 44 has a coating of elastic material 46 and has a bottom diameter greater than that of rows 42, 43 and 45 by au amount Adl. Row 41 also has a coating of elastic material 46 and has a bottom diameter greater than that of row 44 by an amount Ad2, Ad, being approximately equal to Adg. The sprocket wheel of FIGS. 1l and l2 will thus have three contact actions with a chain roller, first by sprocket 41, then by sprocket 44, and last by sprockets 42, 43 and 45.

Similar multi-row sprocket wheels may be provided having a number of rows different than five. Furthermore, the number of contact actions may be other than three. For instance, each row may be spaced, either by phase or by bottom diameter, from every other row. The number of contact actions would then equal the number of rows. Or, alternate rows of sprockets may be equally spaced, either by phase or by bottom diameter, thereby creating two Contact actions. It will be apparent that many such arrangements may be provided.

FIG. 13 shows a single row sprocket wheel of the second embodiment of the present invention. The single row of sprockets is divided in the direction of sprocket width to form two contact surfaces. Contact surface 51 comprises an elastic material and has a bottom diameter greater than the bottom diameter of contact surface 52 by an amount Ad. A single row sprocket wheel divided in the direction of sprocket width may also be constructed according to the first embodiment of the invention. In such a sprocket wheel, the contact surface comprising the elastic material is phased forwardly of the other contact surface.

What is claimed is:

1. A sprocket wheel adapted to mesh with a sprocket chain in a chain drive system, said sprocket wheel comprising a metal base having a plurality of sprockets spaced around the periphery thereof, said sprockets each having at least two surfaces adapted to be contacted by a roller of said sprocket chain, a first of said contact surfaces comprising a surface means of elastic material for causing a rst contact action with said roller and a second of said contact surfaces being integral with said metal base for causing a second contact action with said roller, whereby the collision between said sprocket and said roller is cushioned, and the noise and vibration in said chain drive system is reduced.

2. A sprocket wheel as claimed in claim 1 wherein said wheel comprises a multi-row sprocket wheel, said surface means of elastic material consists of the sprocket surfaces of a portion of the rows of said wheel, and said contact surface integral with said metal base consists of the sprocket surfaces of the remaining rows of said wheel.

3. A sprocket wheel as claimed in claim 2 wherein said portion of the rows of said wheel are out of phase in the direction of rotation of said wheel with said remaining rows of said wheel.

4. A sprocket wheel as claimed in claim 2 wherein said portion of the rows of said wheel have a greater bottom diameter than said remaining rows of said wheel.

5. A sprocket wheel as claimed in claim 1 wherein said wheel comprises a single row sprocket wheel, said wheel is divided into halves in the direction of sprocket width, said surface of elastic material consists of the sprocket surfaces of one of said halves of said divided wheel, and said contact surface means integral with said metal base consists of the sprocket surfaces of the other of said halves of said divided wheel.

6. A sprocket wheel as claimed in claim 5, wherein said one of said halves of said divided wheel is out of phase in the direction of rotation of said wheel with said other of said halves of said divided wheel.

7. A sprocket wheel as claimed in claim 5 wherein said one of said halves of said divided wheel has a greater bottom diameter than said other of said halves of said divided wheel.

8. A sprocket wheel as claimed in claim 1 wherein said surface means of elastic material is out of phase in the direction of rotation of said wheel with said contact surface integral with said -metal base.

9. A sprocket wheel as claimed in claim 1 wherein said surface means of elastic material has a greater bottom diameter than said contact surface integral with said metal base.

10. A chain drive system having a driving sprocket, a driven sprocket and a drive chain mounted around said sprockets, said chain having slack therein; said driving sprocket having a first base wheel, a first surface formed of an elastic material and adapted to contact a first roller of said drive chain in a first contact action, and a second surface integral With said rst base wheel and adapted to contact said first roller in a second contact action, said first surface being out of phase in the direction of rotation of said sprocket with said second surface; and said driven sprocket having a second base wheel, a third surface formed of an elastic material and adapted to contact a second roller of said drive chain in a third contact action, and a fourth surface integral with said second base wheel and adapted to contact said second roller in a fourth contact action, said fourth surface being out of' phase in the direction of rotation of said sprocket with said third surface; whereby collision between the sprockets and chain is cushioned and the noise and vibration in said chain drive system is reduced.

References Cited UNITED STATES PATENTS LEONARD H. GERIN, Primary Examiner U.S. C1. X.R. 

